1. Field of the Invention
The present invention relates to crystal modifiers, and more particularly to crystal modifiers useful as cold flow improvers, pour point depressants, viscosity reducers, paraffin deposition inhibitors and the like for treatment of petroleum and petroleum-derived liquids.
2. Description of the Prior Art
Petroleum (crude oil) as it is produced from underground oil formations often is difficult to handle, particularly in cold weather. For example, it is common that paraffin deposition and/or increased viscosity or pour point render pumping difficult. Similarly, handling difficulties frequently persist in liquids derived from petroleum, such as automotive oils, certain fuels and lubricating oil.
As a result, crystal modifiers are added to such liquids to improve the handling characteristics. In relatively low concentration, the crystal modifier may be used, for example, as cold flow improver or viscosity reducer to improve the flow of liquids such as petroleum and petroleum derived liquids at low temperature. In sufficient concentration, crystal modifiers lower the pour point of the liquid and so often are termed "pour point depressants" in such situations. The crystal modifier also may prevent waxes (paraffin) from building up in production equipment and thereby hindering operations.
Crystal modifiers interfere with crystal formation in fluids and so, depending on the fluid and situation, act as cold flow improvers, pour point depressants, viscosity reducers, paraffin deposition inhibitors and the like. A variety of crystal modifiers are known in the art, and are generally identified by their function, such as cold flow improver, pour point depressant, viscosity reducer or paraffin deposition inhibitor. For example, the dialkylalkenylsuccinates of U.S. Pat. No. 2,561,232 to Rudel et al. and assigned to Standard Oil Development Company have been known as effective pour point depressants for petroleum derived liquids since at least as early as 1951. U.S. Pat. Nos. 3,574,575 and 3,634,052, both of which were assigned to Mobil Corp., and the text, Chemical Additives for Fuels: Developments Since 1978, edited by M. T. Gillies (Noyes Data Corporation 1982), pages 115-152, each of which is incorporated herein by reference, disclose other types of crystal modifiers. Recently, polymer compositions comprising dispersions of at least one olefinically unsaturated compound and containing aliphatic side chains of at least ten carbon atoms (e.g., a polyacrylate or a polyethylene vinyl acetate related product), in a continuous liquid phase comprising at least two surfactants and a liquid polyol was disclosed anonymously in Research Disclosure (July 1995), page 501 (entry 37550), as being effective pour point depressants in crude oil (petroleum) and certain fuel oils. That disclosure calls for removal of the organic solvents, dissolution in glycerin and emulsification in water so that the composition is not hydrocarbon-based.
Conventional crystal modifier technology, however, suffers from various drawbacks in treating petroleum and petroleum-derived liquids. For instance, the active ingredient of crystal modifiers often is a solid or highly viscous liquid. Thus, the active ingredient suffers from the very problems it is intended to solve: it is difficult to handle; that is, removal of the crystal modifier from tanks, whether stationary or on trucks, after storage or transport, and pumping of the crystal modifiers to the locus of treatment can be extremely difficult or impossible.
Therefore, conventional crystal modifier compositions often are low concentration mixtures or solutions of the active ingredient in a solvent, usually an aromatic hydrocarbon such as xylene bottoms. Of course, this resolution in turn raises other disadvantages, including higher costs and difficulties attendant the purchase of large quantities of solvent and attendant the storage, transportation and application of large volumes of liquid for relatively low treatment rates. Moreover, the use of large quantities of solvent also increases the resulting amount of undesirable organic waste. In addition, if the additive composition is a dilute solution, it may have to be added continuously in order to afford continuous treatment. Because continuous treatment requires addition on-site equipment, operation and presence, it is desirable that the composition be added by a batch application, with slow release of the active ingredient affording continuous treatment.
Attempts to respond to the problems encountered in diluting or dissolving the active crystal modifier in large volumes of solvent have included the use of water-in-oil inverse emulsions such as disclosed in U.S. Pat. No. 5,027,901. The composition described in the Research Disclosure article identified above appears to be such a inverse emulsion. However, the reverse emulsions are still very viscous and so do not resolve the handling problem to anywhere close to complete satisfaction. Further, as used conventionally, reverse emulsions have not been known to provide a means for slow release of the active ingredient which could allow continuous treatment from a batch application. Moreover, such prior art compositions require undesirably high flush rates for insertion downhole in oil wells.